Method for indication of sublayer numbers in multilayered video stream

ABSTRACT

A method and device identify a maximum number of temporal sublayers that is allowed in a coded video sequence referring to a parameter set. A coded video sequence is decoded based on the identified maximum number of temporal sublayers that is allowed in the coded video sequence referring to the parameter set.

CROSS-REFERENCES TO RELATED APPLICATION(S)

This application is a continuation application of U.S. application Ser.No. 16/994,004, filed Aug. 14, 2020, which is based on and claimspriority under 35 U.S.C. § 119 to Provisional Application No.63/000,936, filed on Mar. 27, 2020, in the U.S. Patent & TrademarkOffice, the disclosure of which is incorporated by reference herein inits entirety.

FIELD

The disclosed subject matter relates to video coding and decoding, andmore specifically, to output layer derivation in a coded video streamwith multiple layers.

BACKGROUND

Video coding and decoding using inter-picture prediction with motioncompensation has been known for decades. Uncompressed digital video caninclude a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 gigabytes of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reduce aforementioned bandwidth or storage space requirements,in some cases by two orders of magnitude or more. Both lossless andlossy compression, as well as a combination thereof can be employed.Lossless compression refers to techniques where an exact copy of theoriginal signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signal is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision contribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding, some of which will be introducedbelow.

Historically, video encoders and decoders tended to operate on a givenpicture size that was, in most cases, defined and stayed constant for acoded video sequence (CVS), Group of Pictures (GOP), or a similarmulti-picture timeframe. For example, in MPEG-2, system designs areknown to change the horizontal resolution (and, thereby, the picturesize) dependent on factors such as activity of the scene, but only at Ipictures, hence typically for a GOP. The resampling of referencepictures for use of different resolutions within a CVS is known, forexample, from ITU-T Rec. H.263 Annex P. However, here the picture sizedoes not change, only the reference pictures are being resampled,resulting potentially in only parts of the picture canvas being used (incase of downsampling), or only parts of the scene being captured (incase of upsampling). Further, H.263 Annex Q allows the resampling of anindividual macroblock by a factor of two (in each dimension), upward ordownward. Again, the picture size remains the same. The size of amacroblock is fixed in H.263, and therefore does not need to besignaled.

Changes of picture size in predicted pictures became more mainstream inmodern video coding. For example, VP9 allows reference pictureresampling and change of resolution for a whole picture. Similarly,certain proposals made towards VVC (including, for example, Hendry, et.al, “On adaptive resolution change (ARC) for VVC”, Joint Video Teamdocument JVET-M0135-v1, Jan. 9-19, 2019, incorporated herein in itsentirety) allow for resampling of whole reference pictures todifferent—higher or lower—resolutions. In that document, differentcandidate resolutions are suggested to be coded in the sequenceparameter set and referred to by per-picture syntax elements in thepicture parameter set.

SUMMARY

Disclosed are techniques for signaling of adaptive picture size in avideo bitstream.

A method may include identifying a maximum number of temporal sublayersthat is allowed in a coded video sequence referring to a parameter set;and decoding the coded video sequence based on the identified maximumnumber of temporal sublayers that is allowed in the coded video sequencereferring to the parameter set.

A device may include at least one memory configured to store programcode; and at least one processor configured to read the program code andoperate as instructed by the program code, the program code may includeidentifying code configured to cause the processor to identify a maximumnumber of temporal sublayers that is allowed in a coded video sequencereferring to a parameter set; and decoding code that is configured tocause the processor to decode the coded video sequence based on theidentified maximum number of temporal sublayers that is allowed in thecoded video sequence referring to the parameter set.

A non-transitory computer-readable medium may store instructions that,when executed by one or more processors of a device, cause the one ormore processors to identify a maximum number of temporal sublayers thatis allowed in a coded video sequence referring to a parameter set; anddecode the coded video sequence based on the identified maximum numberof temporal sublayers that is allowed in the coded video sequencereferring to the parameter set.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of a simplified block diagram of acommunication system in accordance with an embodiment.

FIGS. 2A and 2B are schematic illustrations of a simplified blockdiagram of a communication system in accordance with an embodiment.

FIG. 3 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 5 is a schematic illustration of options for signaling ARCparameters in accordance with prior art or an embodiment, as indicated.

FIG. 6 is an example of a syntax table in accordance with an embodiment.

FIG. 7 is a schematic illustration of a computer system in accordancewith an embodiment.

FIG. 8 is an example of prediction structure for scalability withadaptive resolution change.

FIG. 9 is an example of a syntax table in accordance with an embodiment.

FIG. 10 is a schematic illustration of a simplified block diagram ofparsing and decoding poc cycle per access unit and access unit countvalue.

FIG. 11 is a schematic illustration of a video bitstream structurecomprising multi-layered sub-pictures.

FIG. 12 is a schematic illustration of a display of the selectedsub-picture with an enhanced resolution.

FIG. 13 is a block diagram of the decoding and display process for avideo bitstream comprising multi-layered sub-pictures.

FIG. 14 is a schematic illustration of 360 video display with anenhancement layer of a sub-picture.

FIG. 15 is an example of a layout information of sub-pictures and itscorresponding layer and picture prediction structure.

FIG. 16 is an example of a layout information of sub-pictures and itscorresponding layer and picture prediction structure, with spatialscalability modality of local region.

FIG. 17 is an example of a syntax table for sub-picture layoutinformation

FIG. 18 is an example of a syntax table of SEI message for sub-picturelayout information.

FIG. 19 is an example of a syntax table to indicate output layers andprofile/tier/level information for each output layer set.

FIG. 20 is an example of a syntax table to indicate output layer mode onfor each output layer set.

FIG. 21 is an example of a syntax table to indicate the presentsubpicture of each layer for each output layer set.

FIG. 22 is an example of a video parameter set RBSP.

FIG. 23 is an example of a sequence parameter set RBSP.

DETAILED DESCRIPTION

When pictures are encoded into a bitstream that includes multiple layerswith different qualities, the bitstream may have syntax elements thatspecify which layers may be outputted at the decoder side. The set oflayers to be outputted is defined as an output layer set. In the latestvideo codec supporting multiple layers and scalabilities, one or moreoutput layer sets are signaled in video parameter set. Those syntaxelements specifying output layer sets and their dependency,profile/tier/level and hypothetical decoder reference model parametersneed to be efficiently signaled in a parameter set.

FIG. 1 illustrates a simplified block diagram of a communication system(100) according to an embodiment of the present disclosure. The system(100) may include at least two terminals (110-120) interconnected via anetwork (150). For unidirectional transmission of data, a first terminal(110) may code video data at a local location for transmission to theother terminal (120) via the network (150). The second terminal (120)may receive the coded video data of the other terminal from the network(150), decode the coded data and display the recovered video data.Unidirectional data transmission may be common in media servingapplications and the like.

FIG. 1 illustrates a second pair of terminals (130, 140) provided tosupport bidirectional transmission of coded video that may occur, forexample, during videoconferencing. For bidirectional transmission ofdata, each terminal (130, 140) may code video data captured at a locallocation for transmission to the other terminal via the network (150).Each terminal (130, 140) also may receive the coded video datatransmitted by the other terminal, may decode the coded data and maydisplay the recovered video data at a local display device.

In FIG. 1 , the terminals (110-140) may be illustrated as servers,personal computers and smart phones but the principles of the presentdisclosure may be not so limited. Embodiments of the present disclosurefind application with laptop computers, tablet computers, media playersand/or dedicated video conferencing equipment. The network (150)represents any number of networks that convey coded video data among theterminals (110-140), including for example wireline and/or wirelesscommunication networks. The communication network (150) may exchangedata in circuit-switched and/or packet-switched channels. Representativenetworks include telecommunications networks, local area networks, widearea networks and/or the Internet. For the purposes of the presentdiscussion, the architecture and topology of the network (150) may beimmaterial to the operation of the present disclosure unless explainedherein below.

FIGS. 2A and 2B illustrate, as an example for an application for thedisclosed subject matter, the placement of a video encoder and decoderin a streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (213), that caninclude a video source (201), for example a digital camera, creating afor example uncompressed video sample stream (202). That sample stream(202), depicted as a bold line to emphasize a high data volume whencompared to encoded video bitstreams, can be processed by an encoder(203) coupled to the camera (201). The encoder (203) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video bitstream (204), depicted as a thin line toemphasize the lower data volume when compared to the sample stream, canbe stored on a streaming server (205) for future use. One or morestreaming clients (206, 208) can access the streaming server (205) toretrieve copies (207, 209) of the encoded video bitstream (204). Aclient (206) can include a video decoder (210) which decodes theincoming copy of the encoded video bitstream (207) and creates anoutgoing video sample stream (211) that can be rendered on a display(212) or other rendering device (not depicted). In some streamingsystems, the video bitstreams (204, 207, 209) can be encoded accordingto certain video coding/compression standards. Examples of thosestandards include ITU-T Recommendation H.265. Under development is avideo coding standard informally known as Versatile Video Coding or VVC.The disclosed subject matter may be used in the context of VVC.

FIG. 3 may be a functional block diagram of a video decoder (210)according to an embodiment of the present invention.

A receiver (310) may receive one or more codec video sequences to bedecoded by the decoder (210); in the same or another embodiment, onecoded video sequence at a time, where the decoding of each coded videosequence is independent from other coded video sequences. The codedvideo sequence may be received from a channel (312), which may be ahardware/software link to a storage device which stores the encodedvideo data. The receiver (310) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (310) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (315) may be coupled inbetween receiver (310) and entropy decoder/parser (320) (“parser”henceforth). When receiver (310) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosychronous network, the buffer (315) may not be needed, or can besmall. For use on best effort packet networks such as the Internet, thebuffer (315) may be required, can be comparatively large and canadvantageously of adaptive size.

The video decoder (210) may include an parser (320) to reconstructsymbols (321) from the entropy coded video sequence. Categories of thosesymbols include information used to manage operation of the decoder(210), and potentially information to control a rendering device such asa display (212) that is not an integral part of the decoder but can becoupled to it, as was shown in FIGS. 2A and 2B. The control informationfor the rendering device(s) may be in the form of SupplementaryEnhancement Information (SEI messages) or Video Usability Information(VUI) parameter set fragments (not depicted). The parser (320) mayparse/entropy-decode the coded video sequence received. The coding ofthe coded video sequence can be in accordance with a video codingtechnology or standard, and can follow principles well known to a personskilled in the art, including variable length coding, Huffman coding,arithmetic coding with or without context sensitivity, and so forth. Theparser (320) may extract from the coded video sequence, a set ofsubgroup parameters for at least one of the subgroups of pixels in thevideo decoder, based upon at least one parameters corresponding to thegroup. Subgroups can include Groups of Pictures (GOPs), pictures, tiles,slices, macroblocks, Coding Units (CUs), blocks, Transform Units (TUs),Prediction Units (PUs) and so forth. The entropy decoder/parser may alsoextract from the coded video sequence information such as transformcoefficients, quantizer parameter values, motion vectors, and so forth.

The parser (320) may perform entropy decoding/parsing operation on thevideo sequence received from the buffer (315), so to create symbols(321).

Reconstruction of the symbols (321) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (320). The flow of such subgroup control information between theparser (320) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, decoder 210 can beconceptually subdivided into a number of functional units as describedbelow. In a practical implementation operating under commercialconstraints, many of these units interact closely with each other andcan, at least partly, be integrated into each other. However, for thepurpose of describing the disclosed subject matter, the conceptualsubdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (351). Thescaler/inverse transform unit (351) receives quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (321) from the parser (320). It can output blockscomprising sample values, that can be input into aggregator (355).

In some cases, the output samples of the scaler/inverse transform (351)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (352). In some cases, the intra pictureprediction unit (352) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current (partly reconstructed) picture(356). The aggregator (355), in some cases, adds, on a per sample basis,the prediction information the intra prediction unit (352) has generatedto the output sample information as provided by the scaler/inversetransform unit (351).

In other cases, the output samples of the scaler/inverse transform unit(351) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a Motion Compensation Prediction unit (353) canaccess reference picture memory (357) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (321) pertaining to the block, these samples can beadded by the aggregator (355) to the output of the scaler/inversetransform unit (in this case called the residual samples or residualsignal) so to generate output sample information. The addresses withinthe reference picture memory form where the motion compensation unitfetches prediction samples can be controlled by motion vectors,available to the motion compensation unit in the form of symbols (321)that can have, for example X, Y, and reference picture components.Motion compensation also can include interpolation of sample values asfetched from the reference picture memory when sub-sample exact motionvectors are in use, motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (355) can be subject to variousloop filtering techniques in the loop filter unit (356). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video bitstream andmade available to the loop filter unit (356) as symbols (321) from theparser (320), but can also be responsive to meta-information obtainedduring the decoding of previous (in decoding order) parts of the codedpicture or coded video sequence, as well as responsive to previouslyreconstructed and loop-filtered sample values.

The output of the loop filter unit (356) can be a sample stream that canbe output to the render device (212) as well as stored in the referencepicture memory (356) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. Once a coded picture is fullyreconstructed and the coded picture has been identified as a referencepicture (by, for example, parser (320)), the current reference picture(356) can become part of the reference picture buffer (357), and a freshcurrent picture memory can be reallocated before commencing thereconstruction of the following coded picture.

The video decoder 320 may perform decoding operations according to apredetermined video compression technology that may be documented in astandard, such as ITU-T Rec. H.265. The coded video sequence may conformto a syntax specified by the video compression technology or standardbeing used, in the sense that it adheres to the syntax of the videocompression technology or standard, as specified in the videocompression technology document or standard and specifically in theprofiles document therein. Also necessary for compliance can be that thecomplexity of the coded video sequence is within bounds as defined bythe level of the video compression technology or standard. In somecases, levels restrict the maximum picture size, maximum frame rate,maximum reconstruction sample rate (measured in, for example megasamplesper second), maximum reference picture size, and so on. Limits set bylevels can, in some cases, be further restricted through HypotheticalReference Decoder (HRD) specifications and metadata for HRD buffermanagement signaled in the coded video sequence.

In an embodiment, the receiver (310) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (320) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or SNR enhancementlayers, redundant slices, redundant pictures, forward error correctioncodes, and so on.

FIG. 4 may be a functional block diagram of a video encoder (203)according to an embodiment of the present disclosure.

The encoder (203) may receive video samples from a video source (201)(that is not part of the encoder) that may capture video image(s) to becoded by the encoder (203).

The video source (201) may provide the source video sequence to be codedby the encoder (203) in the form of a digital video sample stream thatcan be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, .. . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ) and anysuitable sampling structure (for example Y CrCb 4:2:0, Y CrCb 4:4:4). Ina media serving system, the video source (201) may be a storage devicestoring previously prepared video. In a videoconferencing system, thevideo source (203) may be a camera that captures local image informationas a video sequence. Video data may be provided as a plurality ofindividual pictures that impart motion when viewed in sequence. Thepictures themselves may be organized as a spatial array of pixels,wherein each pixel can comprise one or more sample depending on thesampling structure, color space, etc. in use. A person skilled in theart can readily understand the relationship between pixels and samples.The description below focusses on samples.

According to an embodiment, the encoder (203) may code and compress thepictures of the source video sequence into a coded video sequence (443)in real time or under any other time constraints as required by theapplication. Enforcing appropriate coding speed is one function ofController (450). Controller controls other functional units asdescribed below and is functionally coupled to these units. The couplingis not depicted for clarity. Parameters set by controller can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. A person skilled in the art can readily identify other functionsof controller (450) as they may pertain to video encoder (203) optimizedfor a certain system design.

Some video encoders operate in what a person skilled in the are readilyrecognizes as a “coding loop”. As an oversimplified description, acoding loop can consist of the encoding part of an encoder (430)(“source coder” henceforth) (responsible for creating symbols based onan input picture to be coded, and a reference picture(s)), and a (local)decoder (433) embedded in the encoder (203) that reconstructs thesymbols to create the sample data a (remote) decoder also would create(as any compression between symbols and coded video bitstream islossless in the video compression technologies considered in thedisclosed subject matter). That reconstructed sample stream is input tothe reference picture memory (434). As the decoding of a symbol streamleads to bit-exact results independent of decoder location (local orremote), the reference picture buffer content is also bit exact betweenlocal encoder and remote encoder. In other words, the prediction part ofan encoder “sees” as reference picture samples exactly the same samplevalues as a decoder would “see” when using prediction during decoding.This fundamental principle of reference picture synchronicity (andresulting drift, if synchronicity cannot be maintained, for examplebecause of channel errors) is well known to a person skilled in the art.

The operation of the “local” decoder (433) can be the same as of a“remote” decoder (210), which has already been described in detail abovein conjunction with FIG. 3 . Briefly referring also to FIG. 3 , however,as symbols are available and en/decoding of symbols to a coded videosequence by entropy coder (445) and parser (320) can be lossless, theentropy decoding parts of decoder (210), including channel (312),receiver (310), buffer (315), and parser (320) may not be fullyimplemented in local decoder (433).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focusses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

As part of its operation, the source coder (430) may perform motioncompensated predictive coding, which codes an input frame predictivelywith reference to one or more previously-coded frames from the videosequence that were designated as “reference frames.” In this manner, thecoding engine (432) codes differences between pixel blocks of an inputframe and pixel blocks of reference frame(s) that may be selected asprediction reference(s) to the input frame.

The local video decoder (433) may decode coded video data of frames thatmay be designated as reference frames, based on symbols created by thesource coder (430). Operations of the coding engine (432) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 4 ), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (433) replicates decodingprocesses that may be performed by the video decoder on reference framesand may cause reconstructed reference frames to be stored in thereference picture cache (434). In this manner, the encoder (203) maystore copies of reconstructed reference frames locally that have commoncontent as the reconstructed reference frames that will be obtained by afar-end video decoder (absent transmission errors).

The predictor (435) may perform prediction searches for the codingengine (432). That is, for a new frame to be coded, the predictor (435)may search the reference picture memory (434) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(435) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (435), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (434).

The controller (450) may manage coding operations of the video coder(430), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (445). The entropy coder translatesthe symbols as generated by the various functional units into a codedvideo sequence, by loss-less compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter (440) may buffer the coded video sequence(s) as createdby the entropy coder (445) to prepare it for transmission via acommunication channel (460), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(440) may merge coded video data from the video coder (430) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (450) may manage operation of the encoder (203). Duringcoding, the controller (450) may assign to each coded picture a certaincoded picture type, which may affect the coding techniques that may beapplied to the respective picture. For example, pictures often may beassigned as one of the following frame types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other frame in the sequence as a source of prediction.Some video codecs allow for different types of Intra pictures,including, for example Independent Decoder Refresh Pictures. A personskilled in the art is aware of those variants of I pictures and theirrespective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded non-predictively,via spatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codednon-predictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video coder (203) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video coder (203) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (440) may transmit additional datawith the encoded video. The video coder (430) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

Before describing certain aspects of the disclosed subject matter inmore detail, a few terms need to be introduced that will be referred toin the remainder of this description.

Sub-Picture henceforth refers to an, in some cases, rectangulararrangement of samples, blocks, macroblocks, coding units, or similarentities that are semantically grouped, and that may be independentlycoded in changed resolution. One or more sub-pictures may for a picture.One or more coded sub-pictures may form a coded picture. One or moresub-pictures may be assembled into a picture, and one or more subpictures may be extracted from a picture. In certain environments, oneor more coded sub-pictures may be assembled in the compressed domainwithout transcoding to the sample level into a coded picture, and in thesame or certain other cases, one or more coded sub-pictures may beextracted from a coded picture in the compressed domain.

Adaptive Resolution Change (ARC) henceforth refers to mechanisms thatallow the change of resolution of a picture or sub-picture within acoded video sequence, by the means of, for example, reference pictureresampling. ARC parameters henceforth refer to the control informationrequired to perform adaptive resolution change, that may include, forexample, filter parameters, scaling factors, resolutions of outputand/or reference pictures, various control flags, and so forth.

Above description is focused on coding and decoding a single,semantically independent coded video picture. Before describing theimplication of coding/decoding of multiple sub pictures with independentARC parameters and its implied additional complexity, options forsignaling ARC parameters may be described.

Referring to FIG. 5 , shown are several novel options for signaling ARCparameters. As noted with each of the options, they have certainadvantages and certain disadvantages from a coding efficiency,complexity, and architecture viewpoint. A video coding standard ortechnology may choose one or more of these options, or options knownfrom previous art, for signaling ARC parameters. The options may not bemutually exclusive, and conceivably may be interchanged based onapplication needs, standards technology involved, or encoder's choice.

Classes of ARC parameters may include:

-   -   upsample and/or downsample factors, separate or combined in X        and Y dimension    -   upsample and/or downsample factors, with an addition of a        temporal dimension, indicating constant speed zoom in/out for a        given number of pictures    -   Either of the above two may involve the coding of one or more        presumably short syntax elements that may point into a table        containing the factor(s).    -   Resolution, in X or Y dimension, in units of samples, blocks,        macroblocks, CUs, or any other suitable granularity, of the        input picture, output picture, reference picture, coded picture,        combined or separately. If there are more than one resolution        (such as, for example, one for input picture, one for reference        picture) then, in certain cases, one set of values may be        inferred to from another set of values. Such could be gated, for        example, by the use of flags. For a more detailed example, see        below.    -   “Warping” coordinates akin those used in H.263 Annex P, again in        a suitable granularity as described above. H.263 Annex P defines        one efficient way to code such warping coordinates, but other,        potentially more efficient ways could conceivably also be        devised. For example, the variable length reversible,        “Huffman”-style coding of warping coordinates of Annex P could        be replaced by a suitable length binary coding, where the length        of the binary code word could, for example, be derived from a        maximum picture size, possibly multiplied by a certain factor        and offset by a certain value, so to allow for “warping” outside        of the maximum picture size's boundaries.    -   upsample or downsample filter parameters. In the easiest case,        there may be only a single filter for upsampling and/or        downsampling. However, in certain cases, it can be advantageous        to allow more flexibility in filter design, and that may require        to signaling of filter parameters. Such parameters may be        selected through an index in a list of possible filter designs,        the filter may be fully specified (for example through a list of        filter coefficients, using suitable entropy coding techniques),        the filter may be implicitly selected through upsample and/or        downsample ratios according which in turn are signaled according        to any of the mechanisms mentioned above, and so forth.

Henceforth, the description assumes the coding of a finite set ofupsample and/or downsample factors (the same factor to be used in both Xand Y dimension), indicated through a codeword. That codeword canadvantageously be variable length coded, for example using theExt-Golomb code common for certain syntax elements in video codingspecifications such as H.264 and H.265. One suitable mapping of valuesto upsample and/or downsample factors can, for example, be according tothe following table.

TABLE 1 Codeword Ext-Golomb Code Original/Target resolution 0 1 1/1 1010 1/1.5 (upscale by 50%) 2 011 1.5/1 (downscale by 50%) 3 00100 1/2(upscale by 100%) 4 00101 2/1 (downscale by 100%)

Many similar mappings could be devised according to the needs of anapplication and the capabilities of the up and downscale mechanismsavailable in a video compression technology or standard. The table couldbe extended to more values. Values may also be represented by entropycoding mechanisms other than Ext-Golomb codes, for example using binarycoding. That may have certain advantages when the resampling factorswere of interest outside the video processing engines (encoder anddecoder foremost) themselves, for example by MANEs. It should be notedthat, for the (presumably) most common case where no resolution changeis required, an Ext-Golomb code can be chosen that is short; in thetable above, only a single bit. That can have a coding efficiencyadvantage over using binary codes for the most common case.

The number of entries in the table, as well as their semantics may befully or partially configurable. For example, the basic outline of thetable may be conveyed in a “high” parameter set such as a sequence ordecoder parameter set. Alternatively or in addition, one or more suchtables may be defined in a video coding technology or standard, and maybe selected through for example a decoder or sequence parameter set.

Henceforth, we describe how an upsample and/or downsample factor (ARCinformation), coded as described above, may be included in a videocoding technology or standard syntax. Similar considerations may applyto one, or a few, codewords controlling upsample and/or downsamplefilters. See below for a discussion when comparatively large amounts ofdata are required for a filter or other data structures.

H.263 Annex P includes the ARC information 502 in the form of fourwarping coordinates into the picture header 501, specifically in theH.263 PLUSPTYPE (503) header extension. This can be a sensible designchoice when a) there is a picture header available, and b) frequentchanges of the ARC information are expected. However, the overhead whenusing H.263-style signaling can be quite high, and scaling factors maynot pertain among picture boundaries as picture header can be oftransient nature.

JVCET-M135-v1, cited above, includes the ARC reference information (505)(an index) located in a picture parameter set (504), indexing a table(506) including target resolutions that in turn is located inside asequence parameter set (507). The placement of the possible resolutionin a table (506) in the sequence parameter set (507) can, according toverbal statements made by the authors, be justified by using the SPS asan interoperability negotiation point during capability exchange.Resolution can change, within the limits set by the values in the table(506) from picture to picture by referencing the appropriate pictureparameter set (504).

Still referring to FIG. 5 , the following additional options may existto convey ARC information in a video bitstream. Each of those optionshas certain advantages over existing art as described above. The optionsmay be simultaneously present in the same video coding technology orstandard.

In an embodiment, ARC information (509) such as a resampling (zoom)factor may be present in a slice header, GOB header, tile header, ortile group header (tile group header henceforth) (508). This can beadequate of the ARC information is small, such as a single variablelength ue(v) or fixed length codeword of a few bits, for example asshown above. Having the ARC information in a tile group header directlyhas the additional advantage of the ARC information may be applicable toa sub picture represented by, for example, that tile group, rather thanthe whole picture. See also below. In addition, even if the videocompression technology or standard envisions only whole picture adaptiveresolution changes (in contrast to, for example, tile group basedadaptive resolution changes), putting the ARC information into the tilegroup header vis a vis putting it into an H.263-style picture header hascertain advantages from an error resilience viewpoint.

In the same or another embodiment, the ARC information (512) itself maybe present in an appropriate parameter set (511) such as, for example, apicture parameter set, header parameter set, tile parameter set,adaptation parameter set, and so forth (Adaptation parameter setdepicted). The scope of that parameter set can advantageously be nolarger than a picture, for example a tile group. The use of the ARCinformation is implicit through the activation of the relevant parameterset. For example, when a video coding technology or standardcontemplates only picture-based ARC, then a picture parameter set, orequivalent may be appropriate.

In the same or another embodiment, ARC reference information (513) maybe present in a Tile Group header (514) or a similar data structure.That reference information (513) can refer to a subset of ARCinformation (515) available in a parameter set (516) with a scope beyonda single picture, for example a sequence parameter set, or decoderparameter set.

The additional level of indirection implied activation of a PPS from atile group header, PPS, SPS, as used in JVET-M0135-v1 appears to beunnecessary, as picture parameter sets, just as sequence parameter sets,can (and have in certain standards such as RFC3984) be used forcapability negotiation or announcements. If, however, the ARCinformation should be applicable to a sub picture represented, forexample, by a tile groups also, a parameter set with an activation scopelimited to a tile group, such as the Adaptation Parameter Set or aHeader Parameter Set may be the better choice. Also, if the ARCinformation is of more than negligible size—for example contains filtercontrol information such as numerous filter coefficients—then aparameter may be a better choice than using a header (508) directly froma coding efficiency viewpoint, as those settings may be reusable byfuture pictures or sub-pictures by referencing the same parameter set.

When using the sequence parameter set or another higher parameter setwith a scope spanning multiple pictures, certain considerations mayapply:

1. The parameter set to store the ARC information table (516) can, insome cases, be the sequence parameter set, but in other casesadvantageously the decoder parameter set. The decoder parameter set canhave an activation scope of multiple CVSs, namely the coded videostream, i.e. all coded video bits from session start until sessionteardown. Such a scope may be more appropriate because possible ARCfactors may be a decoder feature, possibly implemented in hardware, andhardware features tend not to change with any CVS (which in at leastsome entertainment systems is a Group of Pictures, one second or less inlength). That said, putting the table into the sequence parameter set isexpressly included in the placement options described herein, inparticular in conjunction with point 2 below.

2. The ARC reference information (513) may advantageously be placeddirectly into the picture/slice tile/GOB/tile group header (tile groupheader henceforth) (514) rather than into the picture parameter set asin JVCET-M0135-v1, The reason is as follows: when an encoder wants tochange a single value in a picture parameter set, such as for examplethe ARC reference information, then it has to create a new PPS andreference that new PPS. Assume that only the ARC reference informationchanges, but other information such as, for example, the quantizationmatrix information in the PPS stays. Such information can be ofsubstantial size, and would need to be retransmitted to make the new PPScomplete. As the ARC reference information may be a single codeword,such as the index into the table (513) and that would be the only valuethat changes, it would be cumbersome and wasteful to retransmit all the,for example, quantization matrix information. Insofar, can beconsiderably better from a coding efficiency viewpoint to avoid theindirection through the PPS, as proposed in JVET-M0135-v1. Similarly,putting the ARC reference information into the PPS has the additionaldisadvantage that the ARC information referenced by the ARC referenceinformation (513) necessarily needs to apply to the whole picture andnot to a sub-picture, as the scope of a picture parameter set activationis a picture.

In the same or another embodiment, the signaling of ARC parameters canfollow a detailed example as outlined in FIG. 6 . FIG. 6 depicts syntaxdiagrams in a representation as used in video coding standards since atleast 1993. The notation of such syntax diagrams roughly follows C-styleprogramming. Lines in boldface indicate syntax elements present in thebitstream, lines without boldface often indicate control flow or thesetting of variables.

A tile group header (601) as an exemplary syntax structure of a headerapplicable to a (possibly rectangular) part of a picture canconditionally contain, a variable length, Exp-Golomb coded syntaxelement dec_pic_size_idx (602) (depicted in boldface). The presence ofthis syntax element in the tile group header can be gated on the use ofadaptive resolution (603)—here, the value of a flag not depicted inboldface, which means that flag is present in the bitstream at the pointwhere it occurs in the syntax diagram. Whether or not adaptiveresolution is in use for this picture or parts thereof can be signaledin any high level syntax structure inside or outside the bitstream. Inthe example shown, it is signaled in the sequence parameter set asoutlined below.

Still referring to FIG. 6 , shown is also an excerpt of a sequenceparameter set (610). The first syntax element shown is adaptive_picresolution change flag (611). When true, that flag can indicate the useof adaptive resolution which, in turn may require certain controlinformation. In the example, such control information is conditionallypresent based on the value of the flag based on the if( ) statement inthe parameter set (612) and the tile group header (601).

When adaptive resolution is in use, in this example, coded is an outputresolution in units of samples (613). The numeral 613 refers to bothoutput_pic_width_in_luma_samples and output_pic_height_in_luma_samples,which together can define the resolution of the output picture.Elsewhere in a video coding technology or standard, certain restrictionsto either value can be defined. For example, a level definition maylimit the number of total output samples, which could be the product ofthe value of those two syntax elements. Also, certain video codingtechnologies or standards, or external technologies or standards suchas, for example, system standards, may limit the numbering range (forexample, one or both dimensions must be divisible by a power of 2number), or the aspect ratio (for example, the width and height must bein a relation such as 4:3 or 16:9). Such restrictions may be introducedto facilitate hardware implementations or for other reasons, and arewell known in the art.

In certain applications, it can be advisable that the encoder instructsthe decoder to use a certain reference picture size rather thanimplicitly assume that size to be the output picture size. In thisexample, the syntax element reference_pic_size_present_flag (614) gatesthe conditional presence of reference picture dimensions (615) (again,the numeral refers to both width and height).

Finally, shown is a table of possible decoding picture width andheights. Such a table can be expressed, for example, by a tableindication (num_dec_pic_size_in_luma_samples_minus1) (616). The “minus1”can refer to the interpretation of the value of that syntax element. Forexample, if the coded value is zero, one table entry is present. If thevalue is five, six table entries are present. For each “line” in thetable, decoded picture width and height are then included in the syntax(617).

The table entries presented (617) can be indexed using the syntaxelement dec_pic_size_idx (602) in the tile group header, therebyallowing different decoded sizes—in effect, zoom factors—per tile group.

Certain video coding technologies or standards, for example VP9, supportspatial scalability by implementing certain forms of reference pictureresampling (signaled quite differently from the disclosed subjectmatter) in conjunction with temporal scalability, so to enable spatialscalability. In particular, certain reference pictures may be upsampledusing ARC-style technologies to a higher resolution to form the base ofa spatial enhancement layer. Those upsampled pictures could be refined,using normal prediction mechanisms at the high resolution, so to adddetail.

The disclosed subject matter can be used in such an environment. Incertain cases, in the same or another embodiment, a value in the NALunit header, for example the Temporal ID field, can be used to indicatenot only the temporal but also the spatial layer. Doing so has certainadvantages for certain system designs; for example, existing SelectedForwarding Units (SFU) created and optimized for temporal layer selectedforwarding based on the NAL unit header Temporal ID value can be usedwithout modification, for scalable environments. In order to enablethat, there may be a requirement for a mapping between the coded picturesize and the temporal layer is indicated by the temporal ID field in theNAL unit header.

In some video coding technologies, an Access Unit (AU) can refer tocoded picture(s), slice(s), tile(s), NAL Unit(s), and so forth, thatwere captured and composed into a the respective picture/slice/tile/NALunit bitstream at a given instance in time. That instance in time can bethe composition time.

In HEVC, and certain other video coding technologies, a picture ordercount (POC) value can be used for indicating a selected referencepicture among multiple reference picture stored in a decoded picturebuffer (DPB). When an access unit (AU) comprises one or more pictures,slices, or tiles, each picture, slice, or tile belonging to the same AUmay carry the same POC value, from which it can be derived that theywere created from content of the same composition time. In other words,in a scenario where two pictures/slices/tiles carry the same given POCvalue, that can be indicative of the two picture/slice/tile belonging tothe same AU and having the same composition time. Conversely, twopictures/tiles/slices having different POC values can indicate thosepictures/slices/tiles belonging to different AUs and having differentcomposition times.

In an embodiment of the disclosed subject matter, aforementioned rigidrelationship can be relaxed in that an access unit can comprisepictures, slices, or tiles with different POC values. By allowingdifferent POC values within an AU, it becomes possible to use the POCvalue to identify potentially independently decodablepictures/slices/tiles with identical presentation time. That, in turn,can enable support of multiple scalable layers without a change ofreference picture selection signaling (e.g. reference picture setsignaling or reference picture list signaling), as described in moredetail below.

It is, however, still desirable to be able to identify the AU apicture/slice/tile belongs to, with respect to otherpicture/slices/tiles having different POC values, from the POC valuealone. This can be achieved, as described below.

In the same or other embodiments, an access unit count (AUC) may besignaled in a high-level syntax structure, such as NAL unit header,slice header, tile group header, SEI message, parameter set or AUdelimiter. The value of AUC may be used to identify which NAL units,pictures, slices, or tiles belong to a given AU. The value of AUC may becorresponding to a distinct composition time instance. The AUC value maybe equal to a multiple of the POC value. By diving the POC value by aninteger value, the AUC value may be calculated. In certain cases,division operations can place a certain burden on decoderimplementations. In such cases, small restrictions in the numberingspace of the AUC values may allow to substitute the division operationby shift operations. For example, the AUC value may be equal to a MostSignificant Bit (MSB) value of the POC value range.

In the same embodiment, a value of POC cycle per AU (poc_cycle_au) maybe signaled in a high-level syntax structure, such as NAL unit header,slice header, tile group header, SEI message, parameter set or AUdelimiter. The poc_cycle_au may indicate how many different andconsecutive POC values can be associated with the same AU. For example,if the value of poc_cycle_au is equal to 4, the pictures, slices ortiles with the POC value equal to 0-3, inclusive, are associated withthe AU with AUC value equal to 0, and the pictures, slices or tiles withPOC value equal to 4-7, inclusive, are associated with the AU with AUCvalue equal to 1. Hence, the value of AUC may be inferred by dividingthe POC value by the value of poc_cycle_au.

In the same or another embodiment, the value of poc_cyle_au may bederived from information, located for example in the video parameter set(VPS), that identifies the number of spatial or SNR layers in a codedvideo sequence. Such a possible relationship is briefly described below.While the derivation as described above may save a few bits in the VPSand hence may improves coding efficiency, it can be advantageous toexplicitly code poc_cycle_au in an appropriate high level syntaxstructure hierarchically below the video parameter set, so to be able tominimize poc_cycle_au for a given small part of a bitstream such as apicture. This optimization may save more bits than can be saved throughthe derivation process above because POC values (and/or values of syntaxelements indirectly referring to POC) may be coded in low level syntaxstructures.

In the same or another embodiment, FIG. 9 shows an example of syntaxtables to signal the syntax element of vps_poc_cycle_au in VPS (or SPS),which indicates the poc_cycle_au used for all picture/slices in a codedvideo sequence, and the syntax element of slice_poc_cycle_au, whichindicates the poc_cycle_au of the current slice, in slice header. If thePOC value increases uniformly per AU, vps_contant_poc_cycle_per_au inVPS is set equal to 1 and vps_poc_cycle_au is signaled in VPS. In thiscase, slice_poc_cycle_au is not explicitly signaled, and the value ofAUC for each AU is calculated by dividing the value of POC byvps_poc_cycle_au. If the POC value does not increase uniformly per AU,vps_contant_poc_cycle_per_au in VPS is set equal to 0. In this case,vps_access_unit_cnt is not signaled, while slice_access_unit_cnt issignaled in slice header for each slice or picture. Each slice orpicture may have a different value of slice_access_unit_cnt. The valueof AUC for each AU is calculated by dividing the value of POC byslice_poc_cycle_au. FIG. 10 shows a block diagram illustrating therelevant workflow.

In the same or other embodiments, even though the value of POC of apicture, slice, or tile may be different, the picture, slice, or tilecorresponding to an AU with the same AUC value may be associated withthe same decoding or output time instance. Hence, without anyinter-parsing/decoding dependency across pictures, slices or tiles inthe same AU, all or subset of pictures, slices or tiles associated withthe same AU may be decoded in parallel, and may be outputted at the sametime instance.

In the same or other embodiments, even though the value of POC of apicture, slice, or tile may be different, the picture, slice, or tilecorresponding to an AU with the same AUC value may be associated withthe same composition/display time instance. When the composition time iscontained in a container format, even though pictures correspond todifferent AUs, if the pictures have the same composition time, thepictures can be displayed at the same time instance.

In the same or other embodiments, each picture, slice, or tile may havethe same temporal identifier (temporal_id) in the same AU. All or subsetof pictures, slices or tiles corresponding to a time instance may beassociated with the same temporal sub-layer. In the same or otherembodiments, each picture, slice, or tile may have the same or adifferent spatial layer id (layer_id) in the same AU. All or subset ofpictures, slices or tiles corresponding to a time instance may beassociated with the same or a different spatial layer.

FIG. 8 shows an example of a video sequence structure with combinationof temporal_id, layer_id, POC and AUC values with adaptive resolutionchange. In this example, a picture, slice or tile in the first AU withAUC=0 may have temporal_id=0 and layer_id=0 or 1, while a picture, sliceor tile in the second AU with AUC=1 may have temporal_id=1 andlayer_id=0 or 1, respectively. The value of POC is increased by 1 perpicture regardless of the values of temporal_id and layer_id. In thisexample, the value of poc_cycle_au can be equal to 2. Preferably, thevalue of poc_cycle_au may be set equal to the number of (spatialscalability) layers. In this example, hence, the value of POC isincreased by 2, while the value of AUC is increased by 1.

In the above embodiments, all or sub-set of inter-picture or inter-layerprediction structure and reference picture indication may be supportedby using the existing reference picture set (RPS) signaling in HEVC orthe reference picture list (RPL) signaling. In RPS or RPL, the selectedreference picture is indicated by signaling the value of POC or thedelta value of POC between the current picture and the selectedreference picture. For the disclosed subject matter, the RPS and RPL canbe used to indicate the inter-picture or inter-layer predictionstructure without change of signaling, but with the followingrestrictions. If the value of temporal_id of a reference picture isgreater than the value of temporal_id current picture, the currentpicture may not use the reference picture for motion compensation orother predictions. If the value of layer_id of a reference picture isgreater than the value of layer_id current picture, the current picturemay not use the reference picture for motion compensation or otherpredictions.

In the same and other embodiments, the motion vector scaling based onPOC difference for temporal motion vector prediction may be disabledacross multiple pictures within an access unit. Hence, although eachpicture may have a different POC value within an access unit, the motionvector is not scaled and used for temporal motion vector predictionwithin an access unit. This is because a reference picture with adifferent POC in the same AU is considered a reference picture havingthe same time instance. Therefore, in the embodiment, the motion vectorscaling function may return 1, when the reference picture belongs to theAU associated with the current picture.

In the same and other embodiments, the motion vector scaling based onPOC difference for temporal motion vector prediction may be optionallydisabled across multiple pictures, when the spatial resolution of thereference picture is different from the spatial resolution of thecurrent picture. When the motion vector scaling is allowed, the motionvector is scaled based on both POC difference and the spatial resolutionratio between the current picture and the reference picture.

In the same or another embodiment, the motion vector may be scaled basedon AUC difference instead of POC difference, for temporal motion vectorprediction, especially when the poc_cycle_au has non-uniform value (whenvps_contant_poc_cycle_per_au==0). Otherwise (whenvps_contant_poc_cycle_per_au==1), the motion vector scaling based on AUCdifference may be identical to the motion vector scaling based on POCdifference.

In the same or another embodiment, when the motion vector is scaledbased on AUC difference, the reference motion vector in the same AU(with the same AUC value) with the current picture is not scaled basedon AUC difference and used for motion vector prediction without scalingor with scaling based on spatial resolution ratio between the currentpicture and the reference picture.

In the same and other embodiments, the AUC value is used for identifyingthe boundary of AU and used for hypothetical reference decoder (HRD)operation, which needs input and output timing with AU granularity. Inmost cases, the decoded picture with the highest layer in an AU may beoutputted for display. The AUC value and the layer_id value can be usedfor identifying the output picture.

In an embodiment, a picture may consist of one or more sub-pictures.Each sub-picture may cover a local region or the entire region of thepicture. The region supported by a sub-picture may or may not beoverlapped with the region supported by another sub-picture. The regioncomposed by one or more sub-pictures may or may not cover the entireregion of a picture. If a picture consists of a sub-picture, the regionsupported by the sub-picture is identical to the region supported by thepicture.

In the same embodiment, a sub-picture may be coded by a coding methodsimilar to the coding method used for the coded picture. A sub-picturemay be independently coded or may be coded dependent on anothersub-picture or a coded picture. A sub-picture may or may not have anyparsing dependency from another sub-picture or a coded picture.

In the same embodiment, a coded sub-picture may be contained in one ormore layers. A coded sub-picture in a layer may have a different spatialresolution. The original sub-picture may be spatially re-sampled(up-sampled or down-sampled), coded with different spatial resolutionparameters, and contained in a bitstream corresponding to a layer.

In the same or another embodiment, a sub-picture with (W, H), where Windicates the width of the sub-picture and H indicates the height of thesub-picture, respectively, may be coded and contained in the codedbitstream corresponding to layer 0, while the up-sampled (ordown-sampled) sub-picture from the sub-picture with the original spatialresolution, with (W*S_(w,k), k, H*S_(h,k)), may be coded and containedin the coded bitstream corresponding to layer k, where S_(w,k), S_(h,k)indicate the resampling ratios, horizontally and vertically. If thevalues of S_(w,k), S_(h,k) are greater than 1, the resampling is equalto the up-sampling. Whereas, if the values of S_(w,k), S_(h,k) aresmaller than 1, the resampling is equal to the down-sampling.

In the same or another embodiment, a coded sub-picture in a layer mayhave a different visual quality from that of the coded sub-picture inanother layer in the same sub-picture or different subpicture. Forexample, sub-picture i in a layer, n, is coded with the quantizationparameter, Q_(i,n), while a sub-picture j in a layer, m, is coded withthe quantization parameter, Q_(j,m).

In the same or another embodiment, a coded sub-picture in a layer may beindependently decodable, without any parsing or decoding dependency froma coded sub-picture in another layer of the same local region. Thesub-picture layer, which can be independently decodable withoutreferencing another sub-picture layer of the same local region, is theindependent sub-picture layer. A coded sub-picture in the independentsub-picture layer may or may not have a decoding or parsing dependencyfrom a previously coded sub-picture in the same sub-picture layer, butthe coded sub-picture may not have any dependency from a coded picturein another sub-picture layer.

In the same or another embodiment, a coded sub-picture in a layer may bedependently decodable, with any parsing or decoding dependency from acoded sub-picture in another layer of the same local region. Thesub-picture layer, which can be dependently decodable with referencinganother sub-picture layer of the same local region, is the dependentsub-picture layer. A coded sub-picture in the dependent sub-picture mayreference a coded sub-picture belonging to the same sub-picture, apreviously coded sub-picture in the same sub-picture layer, or bothreference sub-pictures.

In the same or another embodiment, a coded sub-picture consists of oneor more independent sub-picture layers and one or more dependentsub-picture layers. However, at least one independent sub-picture layermay be present for a coded sub-picture. The independent sub-picturelayer may have the value of the layer identifier (layer_id), which maybe present in NAL unit header or another high-level syntax structure,equal to 0. The sub-picture layer with the layer_id equal to 0 is thebase sub-picture layer.

In the same or another embodiment, a picture may consist of one or moreforeground sub-pictures and one background sub-picture. The regionsupported by a background sub-picture may be equal to the region of thepicture. The region supported by a foreground sub-picture may beoverlapped with the region supported by a background sub-picture. Thebackground sub-picture may be a base sub-picture layer, while theforeground sub-picture may be a non-base (enhancement) sub-picturelayer. One or more non-base sub-picture layer may reference the samebase layer for decoding. Each non-base sub-picture layer with layer_idequal to a may reference a non-base sub-picture layer with layer_idequal to b, where a is greater than b.

In the same or another embodiment, a picture may consist of one or moreforeground sub-pictures with or without a background sub-picture. Eachsub-picture may have its own base sub-picture layer and one or morenon-base (enhancement) layers. Each base sub-picture layer may bereferenced by one or more non-base sub-picture layers. Each non-basesub-picture layer with layer_id equal to a may reference a non-basesub-picture layer with layer_id equal to b, where a is greater than b.

In the same or another embodiment, a picture may consist of one or moreforeground sub-pictures with or without a background sub-picture. Eachcoded sub-picture in a (base or non-base) sub-picture layer may bereferenced by one or more non-base layer sub-pictures belonging to thesame sub-picture and one or more non-base layer sub-pictures, which arenot belonging to the same sub-picture.

In the same or another embodiment, a picture may consist of one or moreforeground sub-pictures with or without a background sub-picture. Asub-picture in a layer a may be further partitioned into multiplesub-pictures in the same layer. One or more coded sub-pictures in alayer b may reference the partitioned sub-picture in a layer a.

In the same or another embodiment, a coded video sequence (CVS) may be agroup of the coded pictures. The CVS may consist of one or more codedsub-picture sequences (CSPS), where the CSPS may be a group of codedsub-pictures covering the same local region of the picture. A CSPS mayhave the same or a different temporal resolution than that of the codedvideo sequence.

In the same or another embodiment, a CSPS may be coded and contained inone or more layers. A CSPS may consist of one or more CSPS layers.Decoding one or more CSPS layers corresponding to a CSPS may reconstructa sequence of sub-pictures corresponding to the same local region.

In the same or another embodiment, the number of CSPS layerscorresponding to a CSPS may be identical to or different from the numberof CSPS layers corresponding to another CSPS.

In the same or another embodiment, a CSPS layer may have a differenttemporal resolution (e.g. frame rate) from another CSPS layer. Theoriginal (uncompressed) sub-picture sequence may be temporallyre-sampled (up-sampled or down-sampled), coded with different temporalresolution parameters, and contained in a bitstream corresponding to alayer.

In the same or another embodiment, a sub-picture sequence with the framerate, F, may be coded and contained in the coded bitstream correspondingto layer 0, while the temporally up-sampled (or down-sampled)sub-picture sequence from the original sub-picture sequence, withF*S_(t,k), may be coded and contained in the coded bitstreamcorresponding to layer k, where S_(t,k) indicates the temporal samplingratio for layer k. If the value of S_(t,k) is greater than 1, thetemporal resampling process is equal to the frame rate up conversion.Whereas, if the value of S_(t,k) is smaller than 1, the temporalresampling process is equal to the frame rate down conversion.

In the same or another embodiment, when a sub-picture with a CSPS layera is reference by a sub-picture with a CSPS layer b for motioncompensation or any inter-layer prediction, if the spatial resolution ofthe CSPS layer a is different from the spatial resolution of the CSPSlayer b, decoded pixels in the CSPS layer a are resampled and used forreference. The resampling process may need an up-sampling filtering or adown-sampling filtering.

FIG. 11 shows an example video stream including a background video CSPSwith layer_id equal to 0 and multiple foreground CSPS layers. While acoded sub-picture may consist of one or more CSPS layers, a backgroundregion, which does not belong to any foreground CSPS layer, may consistof a base layer. The base layer may contain a background region andforeground regions, while an enhancement CSPS layer contain a foregroundregion. An enhancement CSPS layer may have a better visual quality thanthe base layer, at the same region. The enhancement CSPS layer mayreference the reconstructed pixels and the motion vectors of the baselayer, corresponding to the same region.

In the same or another embodiment, the video bitstream corresponding toa base layer is contained in a track, while the CSPS layerscorresponding to each sub-picture are contained in a separated track, ina video file.

In the same or another embodiment, the video bitstream corresponding toa base layer is contained in a track, while CSPS layers with the samelayer_id are contained in a separated track. In this example, a trackcorresponding to a layer k includes CSPS layers corresponding to thelayer k, only.

In the same or another embodiment, each CSPS layer of each sub-pictureis stored in a separate track. Each trach may or may not have anyparsing or decoding dependency from one or more other tracks.

In the same or another embodiment, each track may contain bitstreamscorresponding to layer i to layer j of CSPS layers of all or a subset ofsub-pictures, where 0<i=<j=<k, k being the highest layer of CSPS.

In the same or another embodiment, a picture consists of one or moreassociated media data including depth map, alpha map, 3D geometry data,occupancy map, etc. Such associated timed media data can be divided toone or multiple data sub-stream each of which corresponding to onesub-picture.

In the same or another embodiment, FIG. 12 shows an example of videoconference based on the multi-layered sub-picture method. In a videostream, one base layer video bitstream corresponding to the backgroundpicture and one or more enhancement layer video bitstreams correspondingto foreground sub-pictures are contained. Each enhancement layer videbitstream is corresponding to a CSPS layer. In a display, the picturecorresponding to the base layer is displayed by default. It contains oneor more user's picture in a picture (PIP). When a specific user isselected by a client's control, the enhancement CSPS layer correspondingto the selected user is decoded and displayed with the enhanced qualityor spatial resolution. FIG. 13 shows the diagram for the operation.

In the same or another embodiment, a network middle box (such as router)may select a subset of layers to send to a user depending on itsbandwidth. The picture/subpicture organization may be used for bandwidthadaptation. For instance, if the user doesn't have the bandwidth, therouter strips of layers or selects some subpictures due to theirimportance or based on used setup and this can be done dynamically toadopt to bandwidth.

FIG. 14 shows a use case of 360 video. When a spherical 360 picture isprojected onto a planar picture, the projection 360 picture may bepartitioned into multiple sub-pictures as a base layer. An enhancementlayer of a specific sub-picture may be coded and transmitted to aclient. A decoder may be able to decode both the base layer includingall sub-pictures and an enhancement layer of a selected sub-picture.When the current viewport is identical to the selected sub-picture, thedisplayed picture may have a higher quality with the decoded sub-picturewith the enhancement layer. Otherwise, the decoded picture with the baselayer can be displayed, with a low quality.

In the same or another embodiment, any layout information for displaymay be present in a file, as supplementary information (such as SEImessage or metadata). One or more decoded sub-pictures may be relocatedand displayed depending on the signaled layout information. The layoutinformation may be signaled by a streaming server or a broadcaster, ormay be regenerated by a network entity or a cloud server, or may bedetermined by a user's customized setting.

In an embodiment, when an input picture is divided into one or more(rectangular) sub-region(s), each sub-region may be coded as anindependent layer. Each independent layer corresponding to a localregion may have a unique layer_id value. For each independent layer, thesub-picture size and location information may be signaled. For example,picture size (width, height), the offset information of the left-topcorner (x_offset, y_offset). FIG. 15 shows an example of the layout ofdivided sub-pictures, its sub-picture size and position information andits corresponding picture prediction structure. The layout informationincluding the sub-picture size(s) and the sub-picture position(s) may besignaled in a high-level syntax structure, such as parameter set(s),header of slice or tile group, or SEI message.

In the same embodiment, each sub-picture corresponding to an independentlayer may have its unique POC value within an AU. When a referencepicture among pictures stored in DPB is indicated by using syntaxelement(s) in RPS or RPL structure, the POC value(s) of each sub-picturecorresponding to a layer may be used.

In the same or another embodiment, in order to indicate the(inter-layer) prediction structure, the layer_id may not be used and thePOC (delta) value may be used.

In the same embodiment, a sub-picture with a POC vale equal to Ncorresponding to a layer (or a local region) may or may not be used as areference picture of a sub-picture with a POC value equal to N+K,corresponding to the same layer (or the same local region) for motioncompensated prediction. In most cases, the value of the number K may beequal to the maximum number of (independent) layers, which may beidentical to the number of sub-regions.

In the same or another embodiment, FIG. 16 shows the extended case ofFIG. 15 . When an input picture is divided into multiple (e.g. four)sub-regions, each local region may be coded with one or more layers. Inthe case, the number of independent layers may be equal to the number ofsub-regions, and one or more layers may correspond to a sub-region.Thus, each sub-region may be coded with one or more independent layer(s)and zero or more dependent layer(s).

In the same embodiment, in FIG. 16 , the input picture may be dividedinto four sub-regions. The right-top sub-region may be coded as twolayers, which are layer 1 and layer 4, while the right-bottom sub-regionmay be coded as two layers, which are layer 3 and layer 5. In this case,the layer 4 may reference the layer 1 for motion compensated prediction,while the layer 5 may reference the layer 3 for motion compensation.

In the same or another embodiment, in-loop filtering (such as deblockingfiltering, adaptive in-loop filtering, reshaper, bilateral filtering orany deep-learning based filtering) across layer boundary may be(optionally) disabled.

In the same or another embodiment, motion compensated prediction orintra-block copy across layer boundary may be (optionally) disabled.

In the same or another embodiment, boundary padding for motioncompensated prediction or in-loop filtering at the boundary ofsub-picture may be processed optionally. A flag indicating whether theboundary padding is processed or not may be signaled in a high-levelsyntax structure, such as parameter set(s) (VPS, SPS, PPS, or APS),slice or tile group header, or SEI message.

In the same or another embodiment, the layout information ofsub-region(s) (or sub-picture(s)) may be signaled in VPS or SPS. FIG. 17shows an example of the syntax elements in VPS and SPS. In this example,vps_subpicture_dividing_flag is sigalled in VPS. The flag may indicatewhether input picture(s) are divided into multiple sub-regions or not.When the value of vps_subpicture_dividing_flag is equal to 0, the inputpicture(s) in the coded video sequence(s) corresponding to the currentVPS may not be divided into multiple sub-regions. In this case, theinput picture size may be equal to the coded picture size(pic_width_in_luma_samples, pic_height_in_luma_samples), which issignaled in SPS. When the value of vps_subpicture_dividing_flag is equalto 1, the input picture(s) may be divided into multiple sub-regions. Inthis case, the syntax elements vps_full_pic_width_in_luma_samples andvps_full_pic_height_in_luma_samples are signaled in VPS. The values ofvps_full_pic_width_in_luma_samples andvps_full_pic_height_in_luma_samples may be equal to the width and heightof the input picture(s), respectively.

In the same embodiment, the values of vps_full_pic_width_in_luma_samplesand vps_full_pic_height_in_luma_samples may not be used for decoding,but may be used for composition and display.

In the same embodiment, when the value of vps_subpicture_dividing_flagis equal to 1, the syntax elements pic_offset_x and pic_offset_y may besignaled in SPS, which corresponds to (a) specific layer(s). In thiscase, the coded picture size (pic_width_in_luma_samples,pic_height_in_luma_samples) signaled in SPS may be equal to the widthand height of the sub-region corresponding to a specific layer. Also,the position (pic_offset_x, pic_offset_y) of the left-top corner of thesub-region may be signaled in SPS.

In the same embodiment, the position information (pic_offset_x,pic_offset_y) of the left-top corner of the sub-region may not be usedfor decoding, but may be used for composition and display.

In the same or another embodiment, the layout information (size andposition) of all or sub-set sub-region(s) of (an) input picture(s), thedependency information between layer(s) may be signaled in a parameterset or an SEI message. FIG. 18 shows an example of syntax elements toindicate the information o the layout of sub-regions, the dependencybetween layers, and the relation between a sub-region and one or morelayers. In this example, the syntax element num_sub_region indicates thenumber of (rectangular) sub-regions in the current coded video sequence.the syntax element num_layers indicates the number of layers in thecurrent coded video sequence. The value of num_layers may be equal to orgreater than the value of num_sub_region. When any sub-region is codedas a single layer, the value of num_layers may be equal to the value ofnum_sub_region. When one or more sub-regions are coded as multiplelayers, the value of num_layers may be greater than the value ofnum_sub_region. The syntax element direct dependency_flag[i][j]indicates the dependency from the j-th layer to the i-th layer.num_layers_for_region[i] indicates the number of layers associated withthe i-th sub-region. sub region layer_id[i][j] indicates the layer_id ofthe j-th layer associated with the i-th sub-region. Thesub_region_offset_x[i] and sub_region_offset_y[i] indicate thehorizontal and vertical location of the left-top corner of the i-thsub-region, respectively. The sub_region_width [i] andsub_region_height[i] indicate the width and height of the i-thsub-region, respectively.

In one embodiment, one or more syntax elements that specify the outputlayer set to indicate one of more layers to be outputted with or withoutprofile tier level information may be signaled in a high-level syntaxstructure, e.g. VPS, DPS, SPS, PPS, APS or SEI message. Referring toFIG. 19 , the syntax element num_output_layer_sets indicating the numberof output layer set (OLS) in the coded vide sequence referring to theVPS may be signaled in the VPS. For each output layer set,output_layer_flag may be signaled as many as the number of outputlayers.

In the same embodiment, output_layer_flag[i] equal to 1 specifies thatthe i-th layer is output. vps_output_layer_flag[i] equal to 0 specifiesthat the i-th layer is not output.

In the same or another embodiment, one or more syntax elements thatspecify the profile tier level information for each output layer set maybe signaled in a high-level syntax structure, e.g. VPS, DPS, SPS, PPS,APS or SEI message. Still referring to FIG. 19 , the syntax elementnum_profile_tile_level indicating the number of profile tier levelinformation per OLS in the coded vide sequence referring to the VPS maybe signaled in the VPS. For each output layer set, a set of syntaxelements for profile tier level information or an index indicating aspecific profile tier level information among entries in the profiletier level information may be signaled as many as the number of outputlayers.

In the same embodiment, profile_tier_level_idx[i][j] specifies theindex, into the list of profile_tier_level( ) syntax structures in theVPS, of the profile_tier_level( ) syntax structure that applies to thej-th layer of the i-th OLS.

In the same or another embodiment, referring to FIG. 20 , the syntaxelements num_profile_tile_level and/or num_output_layer_sets may besignaled when the number of maximum layers is greater than 1(vps_max_layers_minus1>0).

In the same or another embodiment, referring to FIG. 20 , the syntaxelement vps_output_layers_mode[i] indicating the mode of output layersignaling for the i-th output layer set may be present in VPS.

In the same embodiment, vps_output_layers_mode[i] equal to 0 specifiesthat only the highest layer is output with the i-th output layer set.vps_output_layer_mode[i] equal to 1 specifies that all layers are outputwith the i-th output layer set. vps_output_layer_mode[i] equal to 2specifies that the layers that are output are the layers withvps_output_layer_flag[i][j] equal to 1 with the i-th output layer set.More values may be reserved.

In the same embodiment, the output_layer_flag[i][j] may or may not besignaled depending on the value of vps_output_layers_mode[i] for thei-th output layer set.

In the same or another embodiment, referring to FIG. 20 , theflag_vps_ptl_signal_flag[i] may be present for the i-th output layerset. Depending the value of vps_ptl_signal_flag[i], the profile tierlevel information for the i-th output layer set may or may not besignaled.

In the same or another embodiment, referring to FIG. 21 , the number ofsubpicture, max_subpics_minus1, in the current CVS may be signalled in ahigh-level syntax structure, e.g. VPS, DPS, SPS, PPS, APS or SEImessage.

In the same embodiment, referring to FIG. 21 , the subpictureidentifier, sub_pic_id[i], for the i-th subpicture may be signalled,when the number of subpictures is greater than 1 (max_subpics_minus1>0).

In the same or another embodiment, one or more syntax elementsindicating the subpicture identifier belonging to each layer of eachoutput layer set may be signalled in VPS. Referring to FIG. 22 , thesub_pic_id layer[i][j][k], which indicates the k-th subpicture presentin the j-th layer of the i-th output layer set. With those information,a decoder may recognize which sub-picture may be decoded and outputtedfor each layer of a specific output layer set.

In an embodiment, picture header (PH) is a syntax structure containingsyntax elements that apply to all slices of a coded picture. A pictureunit (PU) is a set of NAL units that are associated with each otheraccording to a specified classification rule, are consecutive indecoding order, and contain exactly one coded picture. A PU may containa picture header (PH) and one or more VCL NAL units composing a codedpicture.

In an embodiment, an SPS (RBSP) may be available to the decoding processprior to it being referenced, included in at least one AU withTemporalId equal to 0 or provided through external means.

In an embodiment, an SPS (RBSP) may be available to the decoding processprior to it being referenced, included in at least one AU withTemporalId equal to 0 in the CVS, which contains one or more PPSreferring to the SPS, or provided through external means.

In an embodiment, an SPS (RBSP) may be available to the decoding processprior to it being referenced by one or more PPS, included in at leastone PU with nuh_layer_id equal to the lowest nuh_layer_id value of thePPS NAL units that refer to the SPS NAL unit in the CVS, which containsone or more PPS referring to the SPS, or provided through externalmeans.

In an embodiment, an SPS (RBSP) may be available to the decoding processprior to it being referenced by one or more PPS, included in at leastone PU with TemporalId equal to 0 and nuh_layer_id equal to the lowestnuh_layer_id value of the PPS NAL units that refer to the SPS NAL unitor provided through external means.

In an embodiment, an SPS (RBSP) may be available to the decoding processprior to it being referenced by one or more PPS, included in at leastone PU with TemporalId equal to 0 and nuh_layer_id equal to the lowestnuh_layer_id value of the PPS NAL units that refer to the SPS NAL unitin the CVS, which contains one or more PPS referring to the SPS, orprovided through external means or provided through external means.

In the same or another embodiment, pps_seq_parameter_set_id specifiesthe value of sps_seq_parameter_set_id for the referenced SPS. The valueof pps_seq_parameter_set_id may be the same in all PPSs that arereferred to by coded pictures in a CLVS.

In the same or another embodiment, all SPS NAL units with a particularvalue of sps_seq_parameter_set_id in a CVS may have the same content.

In the same or another embodiment, regardless of the nuh_layer_idvalues, SPS NAL units may share the same value space ofsps_seq_parameter_set_id.

In the same or another embodiment, the nuh_layer_id value of a SPS NALunit may be equal to the lowest nuh_layer_id value of the PPS NAL unitsthat refer to the SPS NAL unit.

In an embodiment, when an SPS with nuh_layer_id equal to m is referredto by one or more PPS with nuh_layer_id equal to n. the layer withnuh_layer_id equal to m may be the same as the layer with nuh_layer_idequal to n or a (direct or indirect) reference layer of the layer withnuh_layer_id equal to m.

In an embodiment, a PPS (RBSP) may be available to the decoding processprior to it being referenced, included in at least one AU withTemporalId equal to the TemporalId of the PPS NAL unit or providedthrough external means.

In an embodiment, a PPS (RBSP) may be available to the decoding processprior to it being referenced, included in at least one AU withTemporalId equal to the TemporalId of the PPS NAL unit in the CVS, whichcontains one or more PHs (or coded slice NAL units) referring to thePPS, or provided through external means.

In an embodiment, a PPS (RBSP) may be available to the decoding processprior to it being referenced by one or more PHs (or coded slice NALunits), included in at least one PU with nuh_layer_id equal to thelowest nuh_layer_id value of the coded slice NAL units that refer to thePPS NAL unit in the CVS, which contains one or more PHs (or coded sliceNAL units) referring to the PPS, or provided through external means.

In an embodiment, a PPS (RBSP) may be available to the decoding processprior to it being referenced by one or more PHs (or coded slice NALunits), included in at least one PU with TemporalId equal to theTemporalId of the PPS NAL unit and nuh_layer_id equal to the lowestnuh_layer_id value of the coded slice NAL units that refer to the PPSNAL unit in the CVS, which contains one or more PHs (or coded slice NALunits) referring to the PPS, or provided through external means.

In the same or another embodiment, ph_pic_parameter_set_id in PHspecifies the value of pps_pic_parameter_set_id for the referenced PPSin use. The value of pps_seq_parameter_set_id may be the same in allPPSs that are referred to by coded pictures in a CLVS.

In the same or another embodiment, All PPS NAL units with a particularvalue of pps_pic_parameter_set_id within a PU may have the same content.

In the same or another embodiment, regardless of the nuh_layer_idvalues, PPS NAL units may share the same value space ofpps_pic_parameter_set_id.

In the same or another embodiment, the nuh_layer_id value of a PPS NALunit may be equal to the lowest nuh_layer_id value of the coded sliceNAL units that refer to the NAL unit that refer to the PPS NAL unit.

In an embodiment, when a PPS with nuh_layer_id equal to m is referred toby one or more coded slice NAL units with nuh_layer_id equal to n. thelayer with nuh_layer_id equal to m may be the same as the layer withnuh_layer_id equal to n or a (direct or indirect) reference layer of thelayer with nuh_layer_id equal to m.

In an embodiment, a PPS (RBSP) may be available to the decoding processprior to it being referenced, included in at least one AU withTemporalId equal to the TemporalId of the PPS NAL unit or providedthrough external means.

In an embodiment, a PPS (RBSP) may be available to the decoding processprior to it being referenced, included in at least one AU withTemporalId equal to the TemporalId of the PPS NAL unit in the CVS, whichcontains one or more PHs (or coded slice NAL units) referring to thePPS, or provided through external means.

In an embodiment, a PPS (RBSP) may be available to the decoding processprior to it being referenced by one or more PHs (or coded slice NALunits), included in at least one PU with nuh_layer_id equal to thelowest nuh_layer_id value of the coded slice NAL units that refer to thePPS NAL unit in the CVS, which contains one or more PHs (or coded sliceNAL units) referring to the PPS, or provided through external means.

In an embodiment, a PPS (RBSP) may be available to the decoding processprior to it being referenced by one or more PHs (or coded slice NALunits), included in at least one PU with TemporalId equal to theTemporalId of the PPS NAL unit and nuh_layer_id equal to the lowestnuh_layer_id value of the coded slice NAL units that refer to the PPSNAL unit in the CVS, which contains one or more PHs (or coded slice NALunits) referring to the PPS, or provided through external means.

In the same or another embodiment, ph_pic_parameter_set_id in PHspecifies the value of pps_pic_parameter_set_id for the referenced PPSin use. The value of pps_seq_parameter_set_id may be the same in allPPSs that are referred to by coded pictures in a CLVS.

In the same or another embodiment, All PPS NAL units with a particularvalue of pps_pic_parameter_set_id within a PU may have the same content.

In the same or another embodiment, regardless of the nuh_layer_idvalues, PPS NAL units may share the same value space ofpps_pic_parameter_set_id.

In the same or another embodiment, the nuh_layer_id value of a PPS NALunit may be equal to the lowest nuh_layer_id value of the coded sliceNAL units that refer to the NAL unit that refer to the PPS NAL unit.

In an embodiment, when a PPS with nuh_layer_id equal to m is referred toby one or more coded slice NAL units with nuh_layer_id equal to n. thelayer with nuh_layer_id equal to m may be the same as the layer withnuh_layer_id equal to n or a (direct or indirect) reference layer of thelayer with nuh_layer_id equal to m.

Output layer indicates a layer of an output layer set that is output.output layer set (OLS) indicates a set of layers consisting of aspecified set of layers, where one or more layers in the set of layersare specified to be output layers. output layer set (OLS) layer index isan index, of a layer in an OLS, to the list of layers in the OLS.

Sublayer indicates a temporal scalable layer of a temporal scalablebitstream, consisting of VCL NAL units with a particular value of theTemporalId variable and the associated non-VCL NAL units. Sublayerrepresentation indicates a subset of the bitstream consisting of NALunits of a particular sublayer and the lower sublayers.

A VPS RBSP may be available to the decoding process prior to it beingreferenced, included in at least one AU with TemporalId equal to 0 orprovided through external means. All VPS NAL units with a particularvalue of vps_video_parameter_set_id in a CVS may have the same content.FIG. 22 . shows an example of VPS RBSP.

vps_video_parameter_set_id provides an identifier for the VPS forreference by other syntax elements. The value ofvps_video_parameter_set_id may be greater than 0.

vps_max_layers_minus1 plus 1 specifies the maximum allowed number oflayers in each CVS referring to the VPS.

vps_max_sublayers_minus1 plus 1 specifies the maximum number of temporalsublayers that may be present in a layer in each CVS referring to theVPS. The value of vps_max_sublayers_minus1 may be in the range of 0 to6, inclusive.

vps_all_layers_same_num_sublayers_flag equal to 1 specifies that thenumber of temporal sublayers is the same for all the layers in each CVSreferring to the VPS. vps_all_layers_same_num_sublayers_flag equal to 0specifies that the layers in each CVS referring to the VPS may or maynot have the same number of temporal sublayers. When not present, thevalue of vps_all_layers_same_num_sublayers_flag is inferred to be equalto 1.

vps_all_independent_layers_flag equal to 1 specifies that all layers inthe CVS are independently coded without using inter-layer prediction.vps_all_independent_layers_flag equal to 0 specifies that one or more ofthe layers in the CVS may use inter-layer prediction. When not present,the value of vps_all_independent_layers_flag is inferred to be equal to1.

vps_layer_id[i] specifies the nuh_layer_id value of the i-th layer. Forany two non-negative integer values of m and n, when m is less than n,the value of vps_layer_id[m] may be less than vps_layer_id[n].

vps_independent_layer_flag[i] equal to 1 specifies that the layer withindex i does not use inter-layer prediction.vps_independent_layer_flag[i] equal to 0 specifies that the layer withindex i may use inter-layer prediction and the syntax elementsvps_direct_ref_layer_flag[i][j] for j in the range of 0 to i−1,inclusive, are present in VPS. When not present, the value ofvps_independent_layer_flag[i] is inferred to be equal to 1.

vps_direct_ref_layer_flag[i][j] equal to 0 specifies that the layer withindex j is not a direct reference layer for the layer with index i.vps_direct_ref_layer_flag [i][j] equal to 1 specifies that the layerwith index j is a direct reference layer for the layer with index i.When vps_direct_ref_layer_flag[i][j] is not present for i and j in therange of 0 to vps_max_layers_minus1, inclusive, it is inferred to beequal to 0. When vps_independent_layer_flag[i] is equal to 0, there maybe at least one value of j in the range of 0 to i−1, inclusive, suchthat the value of vps_direct_ref_layer_flag[i][j] is equal to 1.

The variables NumDirectRefLayers[i], DirectRefLayerIdx[i][d],NumRefLayers[i], RefLayerIdx[i][r], and LayerUsedAsRefLayerFlag[j] arederived as follows:

for( i = 0; i <= vps_max_layers_minus1; i++ ) {  for( j = 0; j <=vps_max_layers_minus1; j++ ) {   dependencyFlag[ i ][ j ] =vps_direct_ref_layer_flag[ i ][ j ]   for( k = 0; k < i; k++ )    if(vps_direct_ref_layer_flag[ i ][ k ] && dependencyFlag[ k ][ j ] )    dependencyFlag[ i ][ j ] = 1  }  LayerUsedAsRefLayerFlag[ i ] = 0 }for( i = 0; i <= vps_max_layers_minus1; i++ ) {  for( j = 0, d = 0, r =0; j <= vps_max_layers_minus1; j++ ) {   if( vps_direct_ref_layer_flag[i ][ j ] ) {    DirectRefLayerIdx[ i ][ d++ ] = j   LayerUsedAsRefLayerFlag[ j ] = 1   }   if( dependencyFlag[ i ][ j ] )   RefLayerIdx[ i ][ r++ ] = j  }  NumDirectRefLayers[ i ] = d NumRefLayers[ i ] = r }

The variable GeneralLayerIdx[i], specifying the layer index of the layerwith nuh_layer_id equal to vps_layer_id[i], is derived as follows:for(i=0;i<=vps_max_layers_minus1;i++)GeneralLayerIdx[vps_layer_id[i]]=i

For any two different values of i and j, both in the range of 0 tovps_max_layers_minus1, inclusive, when dependencyFlag[i][j] equal to 1,it is a requirement of bitstream conformance that the values ofchroma_format_idc and bit_depth_minus8 that apply to the i-th layer maybe equal to the values of chroma_format_idc and bit_depth_minus8,respectively, that apply to the j-th layer.

max_tid_ref_present_flag[i] equal to 1 specifies that the syntax elementmax_tid_il_ref_pics_plus1[i] is present. max_tid_ref_present_flag[i]equal to 0 specifies that the syntax element max_tid_il_ref_pics_plus1[i] is not present.

max_tid_il_ref_pics_plus1[i] equal to 0 specifies that inter-layerprediction is not used by non-IRAP pictures of the i-th layer.max_tid_il_ref_pics_plus1[i] greater than 0 specifies that, for decodingpictures of the i-th layer, no picture with TemporalId greater thanmax_tid_il_ref_pics_plus1[i]−1 is used as ILRP. When not present, thevalue of max_tid_il_ref_pics_plus1[i] is inferred to be equal to 7.

each_layer_is_an_ols_flag equal to 1 specifies that each OLS containsonly one layer and each layer itself in a CVS referring to the VPS is anOLS with the single included layer being the only output layer.each_layer_is_an_ols_flag equal to 0 that an OLS may contain more thanone layer. If vps_max_layers_minus1 is equal to 0, the value ofeach_layer_is_an_ols_flag is inferred to be equal to 1. Otherwise, whenvps_all_independent_layers_flag is equal to 0, the value ofeach_layer_is_an_ols_flag is inferred to be equal to 0.

ols_mode_idc equal to 0 specifies that the total number of OLSsspecified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLSincludes the layers with layer indices from 0 to i, inclusive, and foreach OLS only the highest layer in the OLS is output.

ols_mode_idc equal to 1 specifies that the total number of OLSsspecified by the VPS is equal to vps_max_layers_minus1+1, the i-th OLSincludes the layers with layer indices from 0 to i, inclusive, and foreach OLS all layers in the OLS are output.

ols_mode_idc equal to 2 specifies that the total number of OLSsspecified by the VPS is explicitly signalled and for each OLS the outputlayers are explicitly signalled and other layers are the layers that aredirect or indirect reference layers of the output layers of the OLS.

The value of ols_mode_idc may be in the range of 0 to 2, inclusive. Thevalue 3 of ols_mode_idc is reserved for future use by ITU-T 1 ISO/IEC.

When vps_all_independent_layers_flag is equal to 1 andeach_layer_is_an_ols_flag is equal to 0, the value of ols_mode_idc isinferred to be equal to 2.

num_output_layer_sets minus1 plus 1 specifies the total number of OLSsspecified by the VPS when ols_mode_idc is equal to 2.

The variable TotalNumOlss, specifying the total number of OLSs specifiedby the VPS, is derived as follows:

  if( vps_max_layers_minus1 = = 0 )  TotalNumOlss = 1 else if(each_layer_is_an_ols_flag | | ols_mode_idc = = 0 | | ols_mode_idc = = 1)  TotalNumOlss = vps_max_layers_minus1 + 1 else if( ols_mode_idc = = 2)  TotalNumOlss = num_output_layer_sets_minus1 + 1

ols_output_layer_flag[i][j] equal to 1 specifies that the layer withnuh_layer_id equal to vps_layer_id[j] is an output layer of the i-th OLSwhen ols_mode_idc is equal to 2. ols_output_layer_flag[i][j] equal to 0specifies that the layer with nuh_layer_id equal to vps_layer_id[j] isnot an output layer of the i-th OLS when ols_mode_idc is equal to 2.

The variable NumOutputLayersInOls[i], specifying the number of outputlayers in the i-th OLS, the variable NumSubLayersInLayerInOLS[i][j],specifying the number of sublayers in the j-th layer in the i-th OLS,the variable OutputLayerIdInOls[i][j], specifying the nuh_layer_id valueof the j-th output layer in the i-th OLS, and the variableLayerUsedAsOutputLayerFlag[k], specifying whether the k-th layer is usedas an output layer in at least one OLS, are derived as follows:

NumOutputLayersInOls[ 0 ] = 1 OutputLayerIdInOls[ 0 ][ 0 ] =vps_layer_id[ 0 ] NumSubLayersInLayerInOLS[ 0 ][ 0 ] =vps_max_sub_layers_minus1 + 1 LayerUsedAsOutputLayerFlag[ 0 ] = 1 for( i= 1, i <= vps_max_layers_minus1; i++ ) {  if( each_layer_is_an_ols_flag| | ols_mode_idc < 2 )   LayerUsedAsOutputLayerFlag[ i ] = 1  else /*(!each_layer_is_an_ols_flag && ols_mode_idc = = 2 ) */  LayerUsedAsOutputLayerFlag[ i ] = 0 } for( i = 1; i < TotalNumOlss;i++ )  if( each_layer_is_an_ols_flag | | ols_mode_idc = = 0 ) {  NumOutputLayersInOls[ i ] = 1   OutputLayerIdInOls[ i ][ 0 ] =vps_layer_id[ i ]   for( j = 0; j < i && ( ols_mode_idc = = 0 ); j++ )   NumSubLayersInLayerInOLS[ i ][ j ] = max_tid_il_ref_pics_plus1[ i ]  NumSubLayersInLayerInOLS[ i ][ i ] = vps_max_sub_layers_minus1 + 1  }else if( ols_mode_idc = = 1 ) {   NumOutputLayersInOls[ i ] = i + 1  for( j = 0; j < NumOutputLayersInOls[ i ]; j++ ) {   OutputLayerIdInOls[ i ][ j ] = vps_layer_id[ j ]   NumSubLayersInLayerInOLS[ i ][ j ] = vps_max_sub_layers_minus1 + 1  }  } else if( ols_mode_idc = = 2 ) {   for( j = 0; j <=vps_max_layers_minus1; j++ ) {    layerIncludedInOlsFlag[ i ][ j ] = 0   NumSubLayersInLayerInOLS[ i ][ j ] = 0   }   for( k = 0, j = 0; k <=vps_max_layers_minus1; k++ )    if( ols_output_layer_flag[ i ][ k ] ) {    layerIncludedInOlsFlag[ i ][ k ] = 1     LayerUsedAsOutputLayerFlag[k ] = 1     OutputLayerIdx[ i ][ j ] = k     OutputLayerIdInOls[ i ][j++ ] = vps_layer_id[ k ]     NumSubLayersInLayerInOLS[ i ][ j ] =vps_max_sub_layers_minus1 + 1    }   NumOutputLayersInOls[ i ] = j  for( j = 0; j < NumOutputLayersInOls[ i ]; j++ ) {    idx =OutputLayerIdx[ i ][ j ]    for( k = 0; k < NumRefLayers[ idx ]; k++ ) {    layerIncludedInOlsFlag[ i ][ RefLayerIdx[ idx ][ k ] ] = 1     if(NumSubLayersInLayerInOLS[ i ][ RefLayerIdx[ idx ][ k ] ] <      max_tid_il_ref_pics_plus1[ OutputLayerIdxInOls[ i ][ j ] ] )     NumSubLayersInLayerInOLS[ i ][ RefLayerIdx[ idx ][ k ] ] =      max_tid_il_ref_pics_plus1[ OutputLayerIdInOls[ i ][ j ] ]    }   } }

For each value of i in the range of 0 to vps_max_layers_minus1,inclusive, the values of LayerUsedAsRefLayerFlag[i] andLayerUsedAsOutputLayerFlag[i] may not be both equal to 0. In otherwords, there may be no layer that is neither an output layer of at leastone OLS nor a direct reference layer of any other layer.

For each OLS, there may be at least one layer that is an output layer.In other words, for any value of i in the range of 0 to TotalNumOlss−1,inclusive, the value of NumOutputLayersInOls[i] may be greater than orequal to 1.

The variable NumLayersInOls[i], specifying the number of layers in thei-th OLS, and the variable LayerIdInOls[i][j], specifying thenuh_layer_id value of the j-th layer in the i-th OLS, are derived asfollows:

  NumLayersInOls[ 0 ] = 1 LayerIdInOls[ 0 ][ 0 ] = vps_layer_id[ 0 ]for( i = 1; i < TotalNumOlss; i++ ) {  if( each_layer_is_an_ols_flag ) {  NumLayersInOls[ i ] = 1   LayerIdInOls[ i ][ 0 ] = vps_layer_id[ i ] } else if( ols_mode_idc = = 0 | | ols_mode_idc = = 1 ) {  NumLayersInOls[ i ] = i + 1   for( j = 0; j < NumLayersInOls[ i ]; j++)    LayerIdInOls[ i ][ j ] = vps_layer_id[ j ]  } else if( ols_mode_idc= = 2 ) {   for( k = 0, j = 0; k <= vps_max_layers_minus1; k++ )    if(layerIncludedInOlsFlag[ i ][ k ] )     LayerIdInOls[ i ][ j++ ] =vps_layer_id[ k ]   NumLayersInOls[ i ] = j  } }

The variable OlsLayerIdx[i][j], specifying the OLS layer index of thelayer with nuh_layer_id equal to LayerIdInOls[i][j], is derived asfollows:

  for( i = 0; i < TotalNumOlss; i++ )  for j = 0; j < NumLayersInOls[ i]; j++ )   OlsLayerIdx[ i ][ LayerIdInOls[ i ][ j ] ] = j

The lowest layer in each OLS may be an independent layer. In otherwords, for each i in the range of 0 to TotalNumOlss−1, inclusive, thevalue of vps_independent_layer_flag[GeneralLayerIdx[LayerIdInOls[i][0]]]may be equal to 1.

Each layer may be included in at least one OLS specified by the VPS. Inother words, for each layer with a particular value of nuh_layer_idnuhLayerId equal to one of vps_layer_id[k] for k in the range of 0 tovps_max_layers_minus1, inclusive, there may be at least one pair ofvalues of i and j, where i is in the range of 0 to TotalNumOlss−1,inclusive, and j is in the range of NumLayersInOls[i]−1, inclusive, suchthat the value of LayerIdInOls[i][j] is equal to nuhLayerId.

In an embodiment, the value of temporalId of any VCL NAL unit in a codedvideo sequence may not be greater than vps_max_sublayers_minus1 in theVPS referred ty by the VCL NAL unit.

In the same or another embodiment, max_tid_il_ref_pics_plus1 [i] has thefollowing semantics:

max_tid_il_ref_pics_plus1[i] equal to 0 specifies that inter-layerprediction is not used by non-IRAP pictures of the i-th layer.max_tid_il_ref_pics_plus1[i] greater than 0 specifies that, for decodingpictures of the i-th layer, no picture with TemporalId greater thanmax_tid_il_ref_pics_plus1 [i]−1 is used as ILRP. When not present, thevalue of max_tid_il_ref_pics_plus1[i] is inferred to be equal tovps_max_sublayers_minus1+1.

In the same or another embodiment, max_tid_il_ref_pics_plus1 [i] may notbe greater than vps_max_sublayers_minus1+1.

In an embodiment, sublayer-wise output layer set may not be derived forindependent layers. Thus, max_tid_il_ref_pics_plus1 andlayerIncludedInOlsFlag may not be derived for independent layers.

In the same another embodiment, the variable NumOutputLayersInOls[i],specifying the number of output layers in the i-th OLS, the variableNumSubLayersInLayerInOLS[i][j], specifying the number of sublayers inthe j-th layer in the i-th OLS, the variable OutputLayerIdInOls[i][j],specifying the nuh_layer_id value of the j-th output layer in the i-thOLS, and the variable LayerUsedAsOutputLayerFlag[k], specifying whetherthe k-th layer is used as an output layer in at least one OLS, arederived as follows:

NumOutputLayersInOls[ 0 ] = 1 OutputLayerIdInOls[ 0 ][ 0 ] =vps_layer_id[ 0 ] NumSubLayersInLayerInOLS[ 0 ][ 0 ] =vps_max_sub_layers_minus1 + 1 LayerUsedAsOutputLayerFlag[ 0 ] = 1 for( i= 1, i <= vps_max_layers_minus1; i++ ) {  if( each_layer_is_an_ols_flag| | ols_mode_idc < 2 )   LayerUsedAsOutputLayerFlag[ i ] = 1  else /*(!each_layer_is_an_ols_flag && ols_mode_idc = = 2 ) */  LayerUsedAsOutputLayerFlag[ i ] = 0 } for( i = 1; i < TotalNumOlss;i++ )  if( each_layer_is_an_ols_flag | | ols_mode_idc = = 0 ) {  NumOutputLayersInOls[ i ] = 1   OutputLayerIdInOls[ i ][ 0 ] =vps_layer_id[ i ]   for( j = 0; j < i && ( ols_mode_idc = = 0 ); j++ )   NumSubLayersInLayerInOLS[ i ][ j ] = max_tid_il_ref_pics_plus1[ i ]  NumSubLayersInLayerInOLS[ i ][ i ] = vps_max_sub_layers_minus1 + 1  }else if( ols_mode_idc = = 1 ) {   NumOutputLayersInOls[ i ] = i + 1  for( j = 0; j < NumOutputLayersInOls[ i ]; j++ ) {   OutputLayerIdInOls[ i ][ j ] = vps_layer_id[ j ]   NumSubLayersInLayerInOLS[ i ][ j ] = vps_max_sub_layers_minus1 + 1  }  } else if( ols_mode_idc = = 2 ) {   for( j = 0; j <=vps_max_layers_minus1; j++ ) {    layerIncludedInOlsFlag[ i ][ j ] = 0   NumSubLayersInLayerInOLS[ i ][ j ] = 0   }   for( k = 0, j = 0; k <=vps_max_layers_minus1; k++ )    if( ols_output_layer_flag[ i ][ k ] ) {    layerIncludedInOlsFlag[ i ][ k ] = 1     LayerUsedAsOutputLayerFlag[k ] = 1     OutputLayerIdx[ i ][ j ] = k     OutputLayerIdInOls[ i ][ j] = vps_layer_id[ k ]     NumSubLayersInLayerInOLS[ i ][ j++ ] =vps_max_sub_layers_minus1 + 1    }   if(!vps_all_independent_layers_flag ) {    NumOutputLayersInOls[ i ] = j   for( j = 0; j < NumOutputLayersInOls[ i ]; j++ ) {     idx =OutputLayerIdx[ i ][ j ]     if( !vps_independent_layer_flag[ idx ] )     for( k = 0; k < NumRefLayers[ idx ]; k++ ) {      layerIncludedInOlsFlag[ i ][ RefLayerIdx[ idx ][ k ] ] = 1      if( NumSubLayersInLayerInOLS[ i ][ RefLayerIdx[ idx ][ k ] ] <        max_tid_il_ref_pics_plus1[ OutputLayerIdInOls[ i ][ j ] ] )       NumSubLayersInLayerInOLS[ i ][ RefLayerIdx[ idx ][ k ] ] =        max_tid_il_ref_pics_plus1[ OutputLayerIdInOls[ i ][ j ] ]      }    }    }   }  }

FIG. 23 shows an example of SPS RBSP syntax table. In the syntaxstructure, sps_max_sublayers_minus1 plus 1 specifies the maximum numberof temporal sublayers that may be present in each CLVS referring to theSPS. The value of sps_max_sublayers_minus1 may be in the range of 0 tovps_max_sublayers_minus1, inclusive.

In an embodiment, when all layers in a coded video sequence have thesame number of sublayers, the number of sublayers of each layer may beequal to the maximum number of sublayers signalled in video parameterset.

In an embodiment, when the value ofvps_all_layers_same_num_sublayers_flag is equal to 1, the value ofsps_max_sublayers_minus1 in SPS referring to the VPS shall be equal tothe value of vps_max_sublayers_minus1.

In an embodiment, when sps_video_parameter_set_id is greater than 0 andvps_all_layers_same_num_sublayers_flag is equal to 1,sps_max_sublayers_minus1 shall be equal to vps_max_sublayers_minus1.

The techniques for signaling adaptive resolution parameters describedabove, can be implemented as computer software using computer-readableinstructions and physically stored in one or more computer-readablemedia. For example, FIG. 7 shows a computer system 700 suitable forimplementing certain embodiments of the disclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by computer central processing units (CPUs),Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 7 for computer system 700 are exemplary innature and are not intended to suggest any limitation as to the scope ofuse or functionality of the computer software implementing embodimentsof the present disclosure. Neither should the configuration ofcomponents be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system 700.

Computer system 700 may include certain human interface input devices.Such a human interface input device may be responsive to input by one ormore human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard 701, mouse 702, trackpad 703, touch screen 710,data-glove 704, joystick 705, microphone 706, scanner 707, camera 708.

Computer system 700 may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen 710, data-glove 704, or joystick 705, but there can also betactile feedback devices that do not serve as input devices), audiooutput devices (such as: speakers 709, headphones (not depicted)),visual output devices (such as screens 710 to include CRT screens, LCDscreens, plasma screens, OLED screens, each with or without touch-screeninput capability, each with or without tactile feedback capability—someof which may be capable to output two dimensional visual output or morethan three dimensional output through means such as stereographicoutput; virtual-reality glasses (not depicted), holographic displays andsmoke tanks (not depicted)), and printers (not depicted).

Computer system 700 can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW720 with CD/DVD or the like media 721, thumb-drive 722, removable harddrive or solid state drive 723, legacy magnetic media such as tape andfloppy disc (not depicted), specialized ROM/ASIC/PLD based devices suchas security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system 700 can also include interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (749) (such as, for example USB ports of thecomputer system 700; others are commonly integrated into the core of thecomputer system 700 by attachment to a system bus as described below(for example Ethernet interface into a PC computer system or cellularnetwork interface into a smartphone computer system). Using any of thesenetworks, computer system 700 can communicate with other entities. Suchcommunication can be uni-directional, receive only (for example,broadcast TV), uni-directional send-only (for example CANbus to certainCANbus devices), or bidirectional, for example to other computer systemsusing local or wide area digital networks. Certain protocols andprotocol stacks can be used on each of those networks and networkinterfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core 740 of thecomputer system 700.

The core 740 can include one or more Central Processing Units (CPU) 741,Graphics Processing Units (GPU) 742, specialized programmable processingunits in the form of Field Programmable Gate Areas (FPGA) 743, hardwareaccelerators for certain tasks 744, and so forth. These devices, alongwith Read-only memory (ROM) 745, Random-access memory 746, internal massstorage such as internal non-user accessible hard drives, SSDs, and thelike 747, may be connected through a system bus 748. In some computersystems, the system bus 748 can be accessible in the form of one or morephysical plugs to enable extensions by additional CPUs, GPU, and thelike. The peripheral devices can be attached either directly to thecore's system bus 748, or through a peripheral bus 749. Architecturesfor a peripheral bus include PCI, USB, and the like.

CPUs 741, GPUs 742, FPGAs 743, and accelerators 744 can execute certaininstructions that, in combination, can make up the aforementionedcomputer code. That computer code can be stored in ROM 745 or RAM 746.Transitional data can be also be stored in RAM 746, whereas permanentdata can be stored for example, in the internal mass storage 747. Faststorage and retrieve to any of the memory devices can be enabled throughthe use of cache memory, that can be closely associated with one or moreCPU 741, GPU 742, mass storage 747, ROM 745, RAM 746, and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture 700, and specifically the core 740 can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core 740 that are of non-transitorynature, such as core-internal mass storage 747 or ROM 745. The softwareimplementing various embodiments of the present disclosure can be storedin such devices and executed by core 740. A computer-readable medium caninclude one or more memory devices or chips, according to particularneeds. The software can cause the core 740 and specifically theprocessors therein (including CPU, GPU, FPGA, and the like) to executeparticular processes or particular parts of particular processesdescribed herein, including defining data structures stored in RAM 746and modifying such data structures according to the processes defined bythe software. In addition or as an alternative, the computer system canprovide functionality as a result of logic hardwired or otherwiseembodied in a circuit (for example: accelerator 744), which can operatein place of or together with software to execute particular processes orparticular parts of particular processes described herein. Reference tosoftware can encompass logic, and vice versa, where appropriate.Reference to a computer-readable media can encompass a circuit (such asan integrated circuit (IC)) storing software for execution, a circuitembodying logic for execution, or both, where appropriate. The presentdisclosure encompasses any suitable combination of hardware andsoftware.

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

The invention claimed is:
 1. A method of decoding video performed by atleast one processor, comprising: identifying a maximum number oftemporal sublayers that is allowed in a coded video sequence referringto a parameter set in a video parameter set (VPS) field and a sequenceparameter set (SPS) field respectively, wherein when a SPS identifierfield, which an identifier for an SPS for reference by other syntaxelements is greater than 0, and when a first syntax element of a VPSindicates that a number of temporal sublayers is the same for all layersin each coded video sequence referring to the VPS, a value of the VPSfield is equal to a value of the SPS field; and decoding the coded videosequence based on the identified maximum number of temporal sublayersthat is allowed in the coded video sequence referring to the parameterset.
 2. The method of claim 1, wherein the temporal sublayers indicatetemporal scalable layers of a temporal scalable bitstream.
 3. The methodof claim 1, further comprising: identifying a maximum number of allowedlayers in the coded video sequence; and decoding the coded videosequence based on the identified maximum number of allowed layers. 4.The method of claim 1, wherein the maximum number of temporal sublayersthat is allowed in the coded video sequence is set in a field of a VPSraw byte sequence payload (RBSP).
 5. The method of claim 4, wherein theVPS RBSP includes a VPS field comprising vps_max_layers_minus1.
 6. Themethod of claim 1, wherein the maximum number of temporal sublayers thatis allowed in the coded video sequence is set in a field of an SPS rawbyte sequence payload (RBSP).
 7. The method of claim 6, wherein the SPSRBSP includes the SPS field comprising sps_max_sublayers_minus1.
 8. Adevice comprising: at least one memory configured to store program code;and at least one processor configured to read the program code andoperate as instructed by the program code, the program code including:identifying code configured to cause the at least one processor toidentify a maximum number of temporal sublayers that is allowed in acoded video sequence referring to a parameter set in a video parameterset (VPS) field and a sequence parameter set (SPS) field respectively,wherein when a SPS identifier field, which an identifier for an SPS forreference by other syntax elements is greater than 0, and when a firstsyntax element of a VPS indicates that a number of temporal sublayers isthe same for all layers in each coded video sequence referring to theVPS, a value of the VPS field is equal to a value of the SPS field; anddecoding code that is configured to cause the at least one processor todecode the coded video sequence based on the identified maximum numberof temporal sublayers that is allowed in the coded video sequencereferring to the parameter set.
 9. The device of claim 8, wherein thetemporal sublayers indicate temporal scalable layers of a temporalscalable bitstream.
 10. The device of claim 8, wherein the identifyingcode is further configured to cause the at least one processor toidentify a maximum number of allowed layers in the coded video sequence,and wherein the decoding code is further configured to cause the atleast one processor to decode the coded video sequence based on theidentified maximum number of allowed layers.
 11. The device of claim 8,wherein the maximum number of temporal sublayers that is allowed in thecoded video sequence is set in a field of a VPS raw byte sequencepayload (RBSP).
 12. The device of claim 11, wherein the VPS RBSPincludes a VPS field comprising vps_max_layers_minus1.
 13. The device ofclaim 8, wherein the maximum number of temporal sublayers that isallowed in the coded video sequence is set in a field of an SPS raw bytesequence payload (RBSP).
 14. The device of claim 13, wherein the SPSRBSP includes the SPS field comprising sps_max_sublayers_minus1.
 15. Anon-transitory computer-readable medium storing instructions, theinstructions comprising: one or more instructions that, when executed byone or more processors of a device, cause the one or more processors to:identify a maximum number of temporal sublayers that is allowed in acoded video sequence referring to a parameter set in a video parameterset (VPS) field and a sequence parameter set (SPS) field respectively,wherein when a SPS identifier field, which an identifier for an SPS forreference by other syntax elements is greater than 0, and when a firstsyntax element of a VPS indicates that a number of temporal sublayers isthe same for all layers in each coded video sequence referring to theVPS, a value of the VPS field is equal to a value of the SPS field; anddecode the coded video sequence based on the identified maximum numberof temporal sublayers that is allowed in the coded video sequencereferring to the parameter set.
 16. The non-transitory computer-readablemedium of claim 15, wherein the temporal sublayers indicate temporalscalable layers of a temporal scalable bitstream.
 17. The non-transitorycomputer-readable medium of claim 15, wherein the one or moreinstructions further cause the one or more processors to: identify amaximum number of allowed layers in the coded video sequence; and decodethe coded video sequence based on the identified maximum number ofallowed layers.
 18. The non-transitory computer-readable medium of claim15, wherein the maximum number of temporal sublayers that is allowed inthe coded video sequence is set in a field of a VPS raw byte sequencepayload (RBSP).
 19. The non-transitory computer-readable medium of claim18, wherein the VPS RBSP includes a VPS field comprisingvps_max_layers_minus1.
 20. The non-transitory computer-readable mediumof claim 15, wherein the maximum number of temporal sublayers that isallowed in the coded video sequence is set in a field of an SPS raw bytesequence payload (RBSP), wherein the SPS RBSP comprisingsps_max_sublayers_minus1.